Solar Energy

The following sections are included:

• Contents
• Foreword to the World Scientific Series on Current Energy Issues

This chapter introduces the sun as our planet's principle and sustainable energy source, noting its main relevant characteristics, and the history as well as pros and cons of its energetic use. It gives a high-level overview of the various solar energy capture and conversion technologies discussed in the book and summarizes the economics and policy aspects.

The present chapter summarizes the current state and perspectives of photovoltaic solar energy. The fundamentals of solar radiation and photovoltaic (solar) cells are covered; the basic technology of photovoltaic modules and systems is briefly discussed; and a general outlook is provided for the uses, market and environmental impact of photovoltaic solar energy.

By concentrating solar radiation a source of heat is provided to generate a hot fluid for a downstream energy conversion process. This can be used to produce electricity, solar fuels or directly use process heat for industry or for chemical applications. The fundamental part of the technology is the solar collector, the most common types being parabolic trough, linear Fresnel, central receiver and paraboloidal dishes. With approximately 4,000MW of solar thermal power plants are presently operating commercially, and 8,000MW of plants are presently at various stages of planning and approval (Status, 2014). The majority of existing plants are parabolic troughs using oil to generate steam for steam turbines. Presently, however, there is a strong emerging interest in central receivers (power towers) due to their ability to produce much higher temperatures at higher efficiency power cycles, and ultimately lower cost. The key for concentrating solar power lies in its ability to incorporate thermal storage and thus provide dispatchable solar power, which will also benefit the penetration of other renewables such as photovoltaic and wind. It is likely that the future for concentrating solar power will involve more high efficiency power cycles and high temperature storage for electricity generation, and solar fuels for transport and industry.

This chapter contains an overview of the main aspects that characterize or have a particular impact on large-scale photovoltaic (PV) power plants. The chapter starts with an introduction and an overview of the megawatts installed in PV plants, and then analyses some key issues in the electrical engineering of plants' layout, devices and grid connection. The chapter also goes through important aspects regarding the behavior, commissioning, operation and maintenance of this type of plants. Several socio-economic factors like policies, planning and regulations, financing tools etc. are considered and a forward-looking view is taken on the prospects for this technology.

Biomass resources and conversion technologies are diverse. Substantial biomass resources exist including woody crops, herbaceous perennials and annuals, forest resources, agricultural residues, and algae. Conversion processes available include fermentation, gasification, pyrolysis, anaerobic digestion, combustion, and transesterification. Bioderived products include liquid fuels (e.g. ethanol, biodiesel, and gasoline and diesel substitutes), gases, electricity, biochemical, and wood pellets. At present the major sources of biomass-derived liquid fuels are from first generation biofuels; ethanol from maize and sugar cane (89 billion liters in 2013) and biodiesel from vegetable oils and fats (24 billion liters in 2011). For other than traditional uses, policy in the forms of mandates, targets, subsidies, and greenhouse gas emission targets has largely been driving biomass utilization. Second generation biofuels have been slow to take off.

Photosynthesis is a natural mechanism which is capable of not only converting solar energy to a potential food stock but also reducing atmospheric CO₂ levels. The process of artificial photosynthesis attempts to mimic this mechanism through the development of materials and technology that can harvest solar energy for high energy conversion to renewable fuel. The potential of using a hugely sustainable source of energy such as solar with H₂O and CO₂, as the only feedstock's, is very desirable in the current global energy situation. A number of approaches have been developed in an attempt to achieve this including; dye sensitized solar cells (DSSCs), photocatalytic H₂O oxidation and CO₂ reduction and nanobiocatalytic complexes. Due to the complexity and intricacy of the interaction between the compounds and structures involved in photosynthesis, replicating the process is faced with a number of challenges; harvesting solar light whilst maintaining a high yield of product, electron transfer and charge separation, carbon fixation and high turnover number. Moreover, photosynthesis is capable of proceeding under a range of varying environmental conditions such as diffuse light conditions. While significant challenges are faced, impressive breakthroughs and advancements have been made in the past decade which contributes towards the development of an artificial photosynthetic system. Discussed herein is the research that has been conducted in artificial photosynthesis covering a range of applications, emerging technologies and the work of dedicated Artificial Photosynthesis System (APS) institutes.

This chapter presents the main technical and non-technical aspects of distributed photovoltaic systems, both grid-connected and stand-alone. In particular, after an introduction where the main typologies and configurations are described, fundamentals on solar resource and operational parameters are presented. Photovoltaic (PV) applications in built areas and stand-alone PV applications will be then covered, including design, sizing, operation and maintenance, business models, policies and international experience.

The applications of harnessing solar energy as heat are presented. The emphasis is on the practical uses of these technologies and their potential for more extensive adoption. Solar water heating, the space heating of buildings, industrial and agricultural process heating together with the many uses of solar cooling are discussed.

Solar radiation is an abundant energy source with high exergy content, suitable for driving thermochemical processes with high efficiency. This chapter provides a comprehensive review of the field of solar thermochemistry, with focus on production of fuels and other chemical commodities. Material, process, and reactor developments for selected processes are discussed along with pertinent advances in thermodynamics, kinetics, and thermal transport.

The following sections are included:

• Index
• About the Contributors